Pneumatic aviation tire

ABSTRACT

Pneumatic tires for aircraft service having a belt package with shoulder reinforcement. The tire includes a belt reinforcing structure or belt package having multiple cut belts, multiple spiral wound belt layers positioned radially between the cut belts and the tread, and multiple spiral wound shoulder layers proximate the shoulder. The spiral wound belt layers and the spiral wound shoulder layers are formed by a continuous cord-reinforced strip having a strip width. The spiral wound belt layers are characterized by a first winding pitch of approximately one strip width per revolution and the spiral wound shoulder layers are characterized by a second winding pitch of less than one strip width per revolution. Alternatively, the spiral wound shoulder layers may be formed with a tiered arrangement by shifting the starting location for successive spiral wound belt layers laterally so that the side edges are not coincident.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/747,835,filed Dec. 29, 2003, now U.S. Pat. No. 7,216,684, the disclosure ofwhich is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to pneumatic tires and, morespecifically, to pneumatic aviation tires for aircraft service havingshoulder reinforcement.

BACKGROUND OF THE INVENTION

Pneumatic aviation tires for service on aircraft landing gears areexposed to severe operating conditions of load and acceleration. Inparticular, pneumatic aviation tires married with the landing gears oflarge commercial airliners are susceptible to severe deformation uponlanding, takeoffs, and controlled movement of the aircraft under its ownpower while on the ground (e.g., taxiing). Loss of a landing gear tireon takeoff (e.g., a blowout) may result in an aborted take-off or anemergency landing. Loss of a tire on the landing gear upon landing mayresult in an inability to halt the airliner's momentum, leading torunway overshoot. Airliners often elevate tire temperature by taxiinglong distances and/or by taxiing fast, which may increase thesusceptibility to blowouts during takeoff or after landing.

Typically, the belt package incorporated into conventional aviationpneumatic tires includes a number of cut belt layers and a number ofspiral wound layers formed from cord reinforced strip(s) wound about thecircumference of the tire with a zero degree spiral overlay. The spiralwound layers terminate proximate the tire shoulder with no overlap asthe winding direction is reversed to apply the successive spiral woundlayers.

One conventional approach for improving tire durability is increase thenumber of belt layers uniformly from crown to shoulder. However, thisapproach results in significant tire weight increases. The tire weightincrease from the added layers is contrary to another tire designparameter for minimizing the net weight of the airliner. Increasing thenumber of belt layers uniformly between the crown and the shoulder alsosignificantly increases the tire's production cost.

For these and other reasons, it would be desirable to provide alightweight pneumatic tire for airliner landing gears characterized byimproved durability and greater load-carrying capability.

SUMMARY OF THE INVENTION

The invention is directed to pneumatic tires for aircraft service thatincludes a carcass, a tread disposed radially outward of the carcass, asidewall intersecting the tread at a shoulder, and a belt reinforcingstructure positioned radially between the carcass and the tread. Thebelt reinforcing structure or belt package includes a plurality of cutbelts, a plurality of spiral wound belt layers positioned radiallybetween the plurality of cut belts and the tread, and a plurality ofspiral wound shoulder layers overlapping the plurality of cut beltsproximate the shoulder. The plurality of spiral wound belt layers andthe plurality of spiral wound shoulder layers are formed by a continuouscord-reinforced strip having a strip width. The plurality of spiralwound belt layers are characterized by a first winding pitch ofapproximately one strip width per revolution and the plurality of spiralwound shoulder layers are characterized by a second winding pitch ofless than one strip width per revolution.

In another embodiment, a pneumatic tire includes a carcass having anequatorial plane, a tread disposed radially outward of the carcass, asidewall intersecting the tread at a shoulder, and a belt reinforcingstructure positioned radially between the carcass and the tread. Thebelt reinforcing structure or belt package includes a plurality of cutbelts and a plurality of spiral wound belt layers positioned radiallybetween the plurality of cut belts and the tread. The spiral wound beltlayers overlap the plurality of cut belts proximate the shoulder. Theplurality of spiral wound belt layers is formed by a continuouscord-reinforced strip having a strip width in which adjacent pairs ofthe plurality of spiral wound belt layers are displaced laterallyrelative to the equatorial plane by a shift distance of less than onestrip width for defining a plurality of overlapping spiral woundshoulder layers proximate the shoulder.

The pneumatic tires of the invention have an improved dynamicperformance produced by adding reinforcement in the cut beltedge/shoulder tire region using a zero degree spiral overlay. Thereinforcement is provided by building up the cut belt edge/shoulderregion by adding overlaid spiral wound strips or spiral layers thatcover the cut belt transverse edges. The additional spiral wound stripsare applied by reducing the pitch of the spiral with which the spiralwound strip is being applied so that the individual turns of the stripare overlapping in the shoulder region, which differs from conventionalspiral wound layers that are nonoverlapping in the shoulder region. Thepneumatic tires of the invention are stiffer in the shoulder region dueto the presence of the additional spiral layers and have increased burststrength. The pneumatic tires of the invention achieve the improvementin dynamic performance and the stiffening without adding significantweight to the as tire, as compared with the conventional approach ofincreasing the number of belt layers uniformly from the crown to theshoulder.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description given below, serve to explain the invention.

FIG. 1 is a diagrammatic view of a belt package of the inventionproviding shoulder reinforcement in an aircraft nose gear tire.

FIG. 2 is a cross-sectional view of a pneumatic tire of an embodiment ofthe invention incorporating the belt package of FIG. 1.

FIG. 3 is an enlarged view of a portion of FIG. 2.

FIG. 4 is a diagrammatic view of a belt package in accordance with analternative embodiment of the invention.

DEFINITIONS

“Axial” and “axially” means the lines or directions that are parallel tothe axis of rotation of the tire.

“Bead” means that part of the tire comprising an annular tensile member

wrapped by ply cords and shaped, with or without other reinforcementelements such as

flippers, chippers, apexes, toe guards and chafers, to fit the designrim.

“Carcass” means the tire structure apart from the belt structure, tread,

undertread, and sidewall rubber over the plies, but including the beads.

“Cord” means one of the reinforcement strands of which the plies in thetire are comprised.

“Crown” refers to substantially the outer circumference of a tire wherethe tread is disposed.

“Circumferential” means circular lines or directions extending along thesurface of the sidewall perpendicular to the axial direction.

“Cut belt or cut breaker reinforcing structure” means at least two cutlayers of plies of parallel cords, woven or unwoven, underlying thetread, unanchored to the bead, and having both left and right cordangles in the range from 10 degrees to 33 degrees with respect to theequatorial plane of the tire.

“Equatorial plane (EP)” means the plane perpendicular to the tire's axisof rotation and passing through the center of its tread.

“Inner” means toward the inside of the tire.

“Lateral” means a direction parallel to the axial direction, as inacross the width of the tread or crown region.

“Outer” means toward the tire's exterior.

“Pneumatic tire” means a laminated mechanical device of generallytoroidal shape, usually an open-torus having beads and a tread and madeof rubber, chemicals, fabric and steel or other materials.

“Radial” and “radially” mean directions radially toward or away from theaxis of rotation of the tire.

“Shoulder” means the upper portion of sidewall just below the treadedge.

“Sidewall” means that portion of a tire between the tread and the beadarea.

“Tread” means a molded rubber component which, when bonded to a tirecasing, includes that portion of the tire that comes into contact withthe road when the tire is normally inflated and under normal load.

DETAILED DESCRIPTION

With reference to FIGS. 1-3, a pneumatic aviation tire 10 suitable forairliner service as a nose gear tire includes a carcass 12, aground-engaging tread 14, a sidewall 16, and a shoulder 18 defined atthe juncture between the sidewall 16 and the tread 14. When mounted onthe nose gear wheel of an airliner, the tread 14 furnishes traction andtire 10 contains a fluid that sustains the airliner load. Pneumaticaviation tire 10 is understood to have mirror symmetry for reflectionabout an equatorial plane 19 bisecting tire 10. Arranged between thecarcass 12 and the tread 14 is a belt package, generally indicated byreference numeral 20, characterized by a plurality of, for example, sixindividual cut belt plies or layers 22, 24, 26, 28, 30, and 32 and aplurality of, for example, two spiral wound belt layers 34, 36positioned radially-outward from the cut belt layers 22, 24, 26, 28, 30and 32. The number of cut belt layers and spiral wound layers in thebelt package 20 may vary according to the tire construction.

As best shown in FIGS. 1 and 3, each of the spiral wound belt layers 34,36 is formed by a continuous rubberized flat strip 38 that is woundcircumferentially (i.e., with a zero degree spiral overlay) about thetire 10 and that extends between the tire shoulders 18. Strip 38 isreinforced with multiple embedded high modulus, essentially inextensiblecords 40 of, for example, nylon, rayon, polyester, aramid, glass, ormetal disposed spatially with a substantially parallel arrangement toone another and covered by a elastomer matrix, such as a cured rubbercasing. The strip width of strip 38 ranges from about 6 mm to about 20mm, typically about 10 mm, the thickness of strip 38 is approximately ofseveral millimeters, and the number of cords 40 per inch is typically inthe range of 18 to 22. During construction of tire 10, the strip 38 iswound circumferentially about a crowned building drum with the strip 38being shifted by a transverse distance approximately equal to, orslightly greater than, the strip width Ws with each individual turn.

The transverse dimensions of the cut belt layers 22, 24, 26, 28, 30 and32 are selected such that their corresponding lateral side edges aretiered or staggered with an overlapping relationship near the shoulder18. For example, cut belt layers 22 and 26 extend laterally for agreater lateral distance from the equatorial plane 19 than cut beltlayer 24 so that the terminal side edge of cut belt layer 24 is coveredby the overlap between layers 22 and 26.

A plurality of overlapping spiral wound shoulder layers 42, 44, 46, 48,50, 52 and 54 are provided in the shoulder 18 of the tire 10. Each ofthe spiral wound shoulder layers 42, 44, and 46 is defined by a singlecircumferential turn of strip 38 in which adjacent turns are shiftedlaterally by less than one strip width (Ws) so that the shoulder layers42, 44, and 46 have a partially overlapping or staggered relationship.In other words, the winding pitch for spiral wound shoulder layers 42,44, and 46 is less than one (1) strip width per revolution. Theremaining spiral wound shoulder layers 48, 50, 52, and 54 are appliedwith a winding pitch equal to one strip width per revolution such thatthere is no overlapping build up in the tire crown region beyond theoverlap afforded by spiral wound belt layers 34, 36. The lateral shiftof less than one strip width is apparent in FIGS. 1-3 as adjacent turnsof strip 38 contribute to the partially overlapping relationship. In acentral region of the shoulder 18, an overlapping relationship isestablished to provide an ultimate thickness equal to six stripthicknesses.

To apply the spiral wound shoulder layers 42, 44, 46, 48, 50, 52 and 54and with continued reference to FIGS. 1-3, the first spiral wound beltlayer 34 is applied to the tire 10. After shoulder layer 54 is applied,the winding pitch is changed from greater than or equal to one stripwidth per revolution (i.e., a zero degree pitch) to a winding pitch thatis less than one (1) strip width per revolution. In the exemplaryembodiment depicted in FIGS. 1-3, the spiral wound shoulder layers 42,44, and 46 are shifted laterally by approximately 0.2 of a strip widthper revolution. The spiral wound shoulder layers 42, 44, and 46 areapplied serially or sequentially from left to right, as best visible inFIG. 1. Spiral wound shoulder layers 48 and 50 are applied with awinding pitch of approximately zero so that shoulder layers 48, 50roughly overlap shoulder layer 48. Then, the winding pitch is revertedto greater than or equal to one strip width per revolution. Spiral woundshoulder layer 52 is applied with the unitary winding pitch of one stripwidth, in an opposite or reverse winding direction from shoulder layers42, 44, and 46. After shoulder layer 52 is applied, the circumferentialturns of strip 38 transition into forming the spiral wound belt layer36. At the opposite shoulder 18, another set of spiral wound shoulderlayers (not shown but similar to spiral wound shoulder layers 42, 44,46, 48, 50, and 52) is applied to tire 10.

With reference to FIG. 4 and in an alternative embodiment of theinvention, a belt package 60 for an aviation pneumatic tire (not shownbut similar to tire 10 (FIGS. 2 and 3)) includes a plurality of cutbelts 62, 64 and a plurality of spiral wound belt layers 66, 68, 70, 72,74, and 76 wound with a zero degree spiral. The laterally outermost turnof spiral wound belt layer 66 is aligned radially with the free sideedge of the underlying cut belt 64. The laterally outermost turn ofspiral wound belt layer 68 is shifted laterally by less than one stripwidth, although the winding pitch remains constant at greater than orequal to about one strip width. Each successive spiral wound belt layer70, 72, 74, and 76 is likewise shifted laterally by less than one stripwidth, although the winding pitch remains constant at greater than orequal to about one strip width. In other words, when the windingdirection is reversed at the turn around positions at each tire shoulder18 (FIG. 1), the initial strip turn of each spiral wound belt layer 66,68, 70, 72, 74, and 76 is shifted laterally by less than one strip widthso that radially adjacent pairs of spiral wound belt layers 66, 68, 70,72, 74, and 76 are only partially overlapping. Alternating spiral woundbelt layers, for example spiral wound belt layers 66, 68, 72, mayinclude multiple overlapping initial turns of strip 38 wound with a zeropitch, although the invention is not so limited. In the exemplaryembodiment, two cut belts and six spiral wound belt layers are providedin the belt package 60, and wherein the shift distance for successivespiral wound belt layers is about 0.33 of the strip width.

The overlapping turns of strip 38 at the lateral edge of the spiralwound belt layers creates a tiered arrangement virtue the lateral shiftin the starting location for successive spiral wound belt layers 66, 68,70, 72, 74, and 76 so that the side edges among successive spiral woundbelt layers 66, 68, 70, 72, 74, and 76 are not coincident. Spiral woundbelt layer 66 contributes three overlapping spiral wound shoulderlayers, spiral wound belt layer 68 contributes one partially overlappingspiral wound shoulder layer, spiral wound belt layer 70 contributesthree partially overlapping spiral wound shoulder layers, etc.

The pneumatic tires 10 of the invention have been observed to complywith the performance standards of Technical Standard Order (TSO) C62dissued by the Federal Aviation Administration without increasing thenumber of belt layers across the full tire width. As a result, therequisite performance standard may be achieved with fewer full-widthbelt layers by adding spiral wound shoulder layers in accordance withthe principles of the invention, which serves to provide a lighter tirealso having standard-complaint performance. More specifically, thespiral wound shoulder layers of the invention provide standard-compliantperformance while permitting a reduction in the number of belt layers.

While the invention has been illustrated by a description of variousembodiments and while these embodiments have been described inconsiderable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Thus, the invention in its broader aspects istherefore not limited to the specific details, representative apparatusand method, and illustrative example shown and described. Accordingly,departures may be made from such details without departing from thespirit or scope of applicant's general inventive concept.

1. A pneumatic tire comprising: a carcass; a tread disposed radiallyoutward of said carcass; a sidewall including a shoulder that intersectssaid tread; and a belt reinforcing structure positioned radially betweensaid carcass and said tread, the belt reinforcing structure including:two cut belts extending axially into said shoulder, six spiral woundbelt layers including a first spiral wound belt layer and a secondspiral wound belt layer, a plurality of overlapping first shoulderlayers with at least one of the first shoulder layers terminating thefirst spiral wound belt layer, and at least one second shoulder layerterminating the second spiral wound belt layer, wherein the first spiralwound belt layer, the second spiral wound belt layer, the plurality ofoverlapping first shoulder layers, and the at least one second shoulderlayer are formed by a continuous cord-reinforced strip having a stripwidth, and the at least one second shoulder layer is shifted relative tothe plurality of overlapping first shoulder layers by a shift distanceof less than one strip width.
 2. The pneumatic tire of claim 1 whereinsaid shift distance is about 0.33 of the strip width.
 3. The pneumatictire of claim 1 wherein said first spiral wound belt layer, said secondspiral wound belt layer, said plurality of overlapping first shoulderlayers, and said at least one second shoulder layer are wound with azero degree spiral overlay.
 4. A pneumatic tire comprising: a carcass; atread disposed radially outward of said carcass; a sidewall including ashoulder that intersects said tread; and a belt reinforcing structurepositioned radially between said carcass and said tread, the beltreinforcing structure including: a plurality of cut belts extendingaxially into said shoulder, a first spiral wound belt layer, a secondspiral wound belt layer, a plurality of overlapping first shoulderlayers with at least one of the first should layers terminating thefirst spiral wound belt layer, and at least one second shoulder layerterminating the second spiral wound belt layer, wherein the first spiralwound belt layer, the second spiral wound belt layer, the plurality ofoverlapping first shoulder layers, and the at least one second shoulderlayer are formed by a continuous cord-reinforced strip having a stripwidth, and the at least one second shoulder layer is shifted relative tothe plurality of overlapping first shoulder layers by a shift distanceof less than one strip width, and said first spiral wound belt layer,said second spiral wound belt layer, said plurality of overlapping firstshoulder layers, and said at least one second shoulder layer are woundwith a zero degree spiral overlay.
 5. The pneumatic tire of claim 4wherein said belt reinforcing structure includes two cut belts and sixspiral wound belt layers.
 6. The pneumatic tire of claim 4 wherein saidshift distance is about 0.33 of the strip width.